PROJECT ABSTRACT This randomized clinical trial will evaluate a novel, piloted, primary palliative care intervention that addresses the lack of advance care planning and psychosocial needs commonly experienced by patients with metastatic cancer.1-8 Up to half of adults with metastatic cancer report elevated anxiety or depression (anx/dep),6,11,12 which can cause withdrawal from daily activities and future planning.13,14 The intervention focuses on patients with elevated anx/dep symptoms?those with highest psychosocial needs who may be at greatest risk for advance care planning non-completion. The intervention is founded on an evidence- based intervention approach known as Acceptance and Commitment Therapy (ACT)11,12 that reduces distress and promotes behavior change through theory-driven mechanisms. 13-17 In a single arm pilot study for adults with metastatic cancer and elevated anx/dep symptoms, we leveraged ACT to design and refine the multi- modal ACT intervention (M-ACT). M-ACT helps patients to live meaningfully and face the future no matter what their health status, including completing advance care planning. In our single-arm pilot study,18 M-ACT was highly rated by patients and was associated with significantly increased advance care planning completion and sense of meaning, and decreased anx/dep symptoms and fear of dying. To increase scalability, M-ACT uses a multi-modal delivery structure that integrates in-person group sessions with online sessions completed at home. Group sessions connect patients to learn in-person together whereas online sessions expand on the skills learned within groups, increasing intervention dose without increasing patient travel or healthcare resource demands. In the proposed randomized trial, we will rigorously compare M-ACT to a usual care control condition. We will also leverage the trial to assess the association between advance care planning and anx/dep symptoms, thereby informing the critical practice question of whether anx/dep symptoms should be addressed concurrently with advance care planning. The proposed study will enroll patients with Stage IV solid tumor cancer (N=240) within the same community-based cancer care network as the pilot study, randomized 1:1 to M-ACT or usual care. We aim to: 1) Evaluate the hypothesis that M-ACT will increase advance care planning completion (primary outcome) and sense of life meaning, and reduce anx/dep symptoms and fear of dying relative to usual care control. 2) Assess the association between anx/dep symptoms and advance care planning at baseline and over time, testing the hypothesis that decreases in anx/dep symptoms at post- intervention will be associated with increases in advance care planning at follow-up. 3) Assess M-ACT's hypothesized mechanisms to specify how the intervention works (exploratory aim). Given their advance care planning and psychosocial needs, and poor access to palliative care, rigorously investigating M-ACT has the potential to benefit community patients with metastatic cancer and to advance palliative care science by addressing gaps in novel approaches, foundational knowledge, and the scalable delivery of palliative care. !